Hybrid slab waterproofs underground car park

The challenge

The foundation slab lies 10 m below the water table and forms a raft that must be capable of resisting upward water pressure and movement. The slab was therefore required to have a maximum crack width of just 0.11 mm.

The solution

Achieving the required crack limitation was almost impossible with traditional rebar mesh reinforcement. Bekaert proposed a hybrid solution using top and bottom rebar mesh in single (not double) layers supplemented by steel fiber reinforcement. This solution not only met the technical requirements but was also more cost-effective. Less rebar cuts the time and labor involved in steel fixing, and wider spacing of the rebar

The 400 mm thick raft was cast in four sections (a day for each) totaling around 7,000 m2.